Extracting files from a Zip archive programmatically using C# and System.IO.Packaging

Question

I have a bunch of ZIP files that are in desperate need of some hierarchical reorganization and extraction. What I can do, currently, is create the directory structure and move the zip files to the proper location. The mystic cheese that I am missing is the part that extracts the files from the ZIP archive.

I have seen the MSDN articles on the ZipArchive class and understand them reasonable well. I have also seen the VBScript ways to extract. This is not a complex class so extracting stuff should be pretty simple. In fact, it works "mostly". I have included my current code below for reference.

 using (ZipPackage package = (ZipPackage)Package.Open(@"..\..\test.zip", FileMode.Open, FileAccess.Read))
 {
    PackagePartCollection packageParts = package.GetParts();
    foreach (PackageRelationship relation in packageParts)
    {
       //Do Stuff but never gets here since packageParts is empty.
    }
 }

The problem seems to be somewhere in the GetParts (or Get*Anything* for that matter). It seems that the package, while open, is empty. Digging deeper the debugger shows that the private member _zipArchive shows that it actually has parts. Parts with the right names and everything. Why won't the GetParts function retrieve them? I'ver tried casting the open to a ZipArchive and that didn't help. Grrr.

Answer 1

From MSDN,

In this sample, the Package class is used (as opposed to the ZipPackage.) Having worked with both, I've only seen flakiness happen when there's corruption in the zip file. Not necessarily corruption that throws the Windows extractor or Winzip, but something that the Packaging components have trouble handling.

Hope this helps, maybe it can provide you an alternative to debugging the issue.

using System;
using System.IO;
using System.IO.Packaging;
using System.Text;

class ExtractPackagedImages
{
    static void Main(string[] paths)
    {
        foreach (string path in paths)
        {
            using (Package package = Package.Open(
                path, FileMode.Open, FileAccess.Read))
            {
                DirectoryInfo dir = Directory.CreateDirectory(path + " Images");
                foreach (PackagePart part in package.GetParts())
                {
                    if (part.ContentType.ToLowerInvariant().StartsWith("image/"))
                    {
                        string target = Path.Combine(
                            dir.FullName, CreateFilenameFromUri(part.Uri));
                        using (Stream source = part.GetStream(
                            FileMode.Open, FileAccess.Read))
                        using (Stream destination = File.OpenWrite(target))
                        {
                            byte[] buffer = new byte[0x1000];
                            int read;
                            while ((read = source.Read(buffer, 0, buffer.Length)) > 0)
                            {
                                destination.Write(buffer, 0, read);
                            }
                        }
                        Console.WriteLine("Extracted {0}", target);
                    }
                }
            }
        }
        Console.WriteLine("Done");
    }

    private static string CreateFilenameFromUri(Uri uri)
    {
        char [] invalidChars = Path.GetInvalidFileNameChars();
        StringBuilder sb = new StringBuilder(uri.OriginalString.Length);
        foreach (char c in uri.OriginalString)
        {
            sb.Append(Array.IndexOf(invalidChars, c) < 0 ? c : '_');
        }
        return sb.ToString();
    }
}

Answer 2

From "ZipPackage Class" (MSDN):

While Packages are stored as Zip files* through the ZipPackage class, all Zip files are not ZipPackages. A ZipPackage has special requirements such as URI-compliant file (part) names and a "[Content_Types].xml" file that defines the MIME types for all the files contained in the Package. The ZipPackage class cannot be used to open arbitary Zip files that do not conform to the Open Packaging Conventions standard.

For further details see Section 9.2 "Mapping to a ZIP Archive" of the ECMA International "Open Packaging Conventions" standard, http://www.ecma-international.org/publications/files/ECMA-ST/Office%20Open%20XML%20Part%202%20(DOCX).zip (342Kb) or http://www.ecma-international.org/publications/files/ECMA-ST/Office%20Open%20XML%20Part%202%20(PDF).zip (1.3Mb)

*You can simply add ".zip" to the extension of any ZipPackage-based file (.docx, .xlsx, .pptx, etc.) to open it in your favorite Zip utility.

Answer 3

If you are manipulating ZIP files, you may want to look into a 3rd-party library to help you.

For example, DotNetZip, which has been recently updated. The current version is now v1.8. Here's an example to create a zip:

using (ZipFile zip = new ZipFile())
{
  zip.AddFile("c:\\photos\\personal\\7440-N49th.png");
  zip.AddFile("c:\\Desktop\\2005_Annual_Report.pdf");
  zip.AddFile("ReadMe.txt");

  zip.Save("Archive.zip");
}

Here's an example to update an existing zip; you don't need to extract the files to do it:

using (ZipFile zip = ZipFile.Read("ExistingArchive.zip"))
{
  // 1. remove an entry, given the name
  zip.RemoveEntry("README.txt");

  // 2. Update an existing entry, with content from the filesystem
  zip.UpdateItem("Portfolio.doc");

  // 3. modify the filename of an existing entry 
  // (rename it and move it to a sub directory)
  ZipEntry e = zip["Table1.jpg"];
  e.FileName = "images/Figure1.jpg";

  // 4. insert or modify the comment on the zip archive
  zip.Comment = "This zip archive was updated " + System.DateTime.ToString("G"); 

  // 5. finally, save the modified archive
  zip.Save();
}

here's an example that extracts entries:

using (ZipFile zip = ZipFile.Read("ExistingZipFile.zip"))
{
  foreach (ZipEntry e in zip)
  {
    e.Extract(TargetDirectory, true);  // true => overwrite existing files
  }
}

DotNetZip supports multi-byte chars in filenames, Zip encryption, AES encryption, streams, Unicode, self-extracting archives. Also does ZIP64, for file lengths greater than 0xFFFFFFFF, or for archives with more than 65535 entries.

free. open source

get it at codeplex

Answer 4

I agree withe Cheeso. System.IO.Packaging is awkward when handling generic zip files, seeing as it was designed for Office Open XML documents. I'd suggest using DotNetZip or SharpZipLib